• Title/Summary/Keyword: water table

Search Result 735, Processing Time 0.025 seconds

Evaluation of Ground Water Level Effect on Frost Heaving in Road Pavements (도로 포장체에서 동상에 대한 지하수위 영향 평가)

  • Kweon, Gichul;Lee, Jaehoan
    • International Journal of Highway Engineering
    • /
    • v.15 no.1
    • /
    • pp.47-56
    • /
    • 2013
  • PURPOSES: This study is to evaluate a ground water level effect on frost heaving in road pavements. METHODS: The effects of water table on frost heaving in pavement systems were evaluated from the mechanical analysis using FROST program. The input parameters and boundary conditions were determined by considering climates, pavement sections, and material properties specially subgrade soil types in Korea. RESULTS: When the water table located above the freezing depth, amount of frost heaving caused by freezing the water in pavement itself was big enough to damage in pavement system, although pavement system consists of fully non-frost-susceptible materials with sufficient thickness of anti-freezing layer. The amount of frost heaving was decreased rapidly with increasing the distance between the water table and freezing depth. CONCLUSIONS: It was concluded that there is no engineering problems related with frost heaving in practical sense when the distance between freezing depth and water table is over 1.5m for having subgrade soils less than 50% of #200 sieve passing to meet specification on quality control in Korea.

Water table: The dominant control on CH4 and CO2 emission from a closed landfill site

  • Nwachukwu, Arthur N.;Nwachukwu, Nkechinyere V.
    • Advances in environmental research
    • /
    • v.9 no.2
    • /
    • pp.123-133
    • /
    • 2020
  • A time series dataset was conducted to ascertain the effect of water table on the variability in and emission of CH4 and CO2 concentrations at a closed landfill site. An in-situ data of methane/carbon dioxide concentrations and environmental parameters were collected by means of an in-borehole gas monitor, the Gasclam (Ion Science, UK). Linear regression analysis was used to determine the strength of the correlation between ground-gas concentration and water table. The result shows CH4 and CO2 concentrations to be variable with strong negative correlations of approximately 0.5 each with water table over the entire monitoring period. The R2 was slightly improved by considering their concentration over single periods of increasing and decreasing water table, single periods of increasing water table, and single periods of decreasing water table; their correlations increased significantly at 95% confidence level. The result revealed that fluctuations in groundwater level is the key driving force on the emission of and variability in groundgas concentration and neither barometric pressure nor temperature. This finding further validates the earlier finding that atmospheric pressure - the acclaimed major control on the variability/migration of CH4 and CO2 concentrations on contaminated sites, is not always so.

A Modification of Water Table Fluctuation Model Considering Delayed Drainage Effect of Unsaturated Zone (비포화대 지연배수 효과를 고려한 지하수위 변동모델의 개선 및 적용)

  • Kim, Seong-Han;Park, Eun-Gyu;Kim, Yong-Sung;Kim, Nam-Jin
    • Journal of Soil and Groundwater Environment
    • /
    • v.16 no.3
    • /
    • pp.17-27
    • /
    • 2011
  • Recently, a physically based model of water-table fluctuation due to precipitation is developed based on aquifer water balance model. In the model, it was assumed that the water infiltration into ground surface is advection dominant and immediately reaches to water-table. The assumption may be suited for the sites where the water-table is shallow and/or the permeability of the unsaturated zone is high. However, there are more cases where the model is not directly applicable due to thick and low permeable unsaturated zone. For the low permeability unsaturated zone, the pattern of water flux passing through unsaturated zone is diffusive as well as advective. In this study, to improve the previously developed water-table fluctuation model, we combined the delayed drainage model, which has long been used in well hydraulics, to the water-table fluctuation model. To test the validity of the development, we apply the developed model to 5 different domestic sites. The model parameters are calibrated based on the groundwater hydrograph and the precipitation time series, and the correlation analyses among the parameters are pursued. The overall analyses on the delineated model parameters indicate that the delayed drainage parameters or delay index used in the developed model are able to reveal drainage information in the unsaturated zones.

Effects of Water Table Depth in Different Soil Texture on Growth and Yield of Barley and Wheat (토성별 지하수위가 밀, 보리의 생육 및 수량에 미치는 영향)

  • 이홍석;박의호;송현숙;구자환
    • KOREAN JOURNAL OF CROP SCIENCE
    • /
    • v.40 no.2
    • /
    • pp.195-202
    • /
    • 1995
  • This experiment was performed to characterize the optimum water table level for the growth and yield of barley(var. Olbori) and wheat(var, Grumil), Olbori and Grumil were grown in the 550 liter plastic pot filled with silt loam or sandy loam, During the whole growth period, the water table adjusted to be 20, 30, 40, 50, and 70cm, Higher water table was resulted in the decrease in plant height and top dry weight, but in the increase of the ratio of top to root dry weight, especially in barley, This suggested that high water table level affected more the growth of top than that of root, The number and area of green leaves were decreased as the water table was higher than 30 to 40cm at the late growth period(May 18, 1993), The largest number and area of green leaves were shown at 50cm of water table in sandy loam and at 70cm in silt loam, As the water table was high, the leaf chlorophyll content was low, And barley was affected more significantly than wheat by soil texture, The photosynthetic activity was decreased remarkably at 20cm water table, Heading period was 2 to 3 and 4 days earlier at the 20cm water table of sandy loam in barley and wheat, respectively, However this earlier heading was not shown in silt loam, Grain filling was accelerated 5 to 7 days earlier in barley and 10 days in wheat grown at 20cm water table, The highest yield was present at 50 and 70cm water table, The yield was decreased remarkably at 20cm water table, resulting that yield reduction ratio of barley was 71.1% and 72, 2%, and that of wheat was 41.0% and 60, 0% in sandy loam and silt loam, respectively, High water table decreased the number of spike per unit area, but increased the seed weight per spike in barley, However, High water table reduced the seed weight per spike in wheat. There was significant correlation between yield and leaf chlorophyll content in wheat and barley, Yield was correlated significantly with green leaf area in barley, and with top dry weight, ratio of top to root dry weight chlorophyll content and photosynthetic activity in wheat. The optimum water table was 50 to 70cm in wheat and barley, They grew fairly well at 30cm water table of sandy loam, and at 40cm of silt loam.

  • PDF

Variational Characteristics of Water-Table and Soil Moisture in Paddy-Upland Rotational Fields (전전환답 포장에서의 지하수위 및 토양수분 변화 특성)

  • 권순국;윤경섭
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.36 no.2
    • /
    • pp.123-131
    • /
    • 1994
  • Experimental studies were conducted to make clear the soil moisture environment under the condition of paddy-upland rotational fields by investigating water-table depths and soil moisture contents during growing season of crops in two kinds of soil. The following results were obtained. 1.Although water-table depths fluctuated with the amount of rainfall in the experimental field, it seemed that the variation of vater4able depths in the paddy-upland rotational, field was strongly affected by the condition of locations on paddy fields. 2.It is recognized that the concept of sum of excess water depth(SEWxx) and sum of excess water day(SEDxx) can be used to represent the soil moisture stress index due to the fluctuation of water-table depths. 3.The results of this study clearly indicate that drainage in paddy-upland rotational field to maintain an optimum soil moisture content must be made by introducing the concept of block drainage which needs both subsurface drainage and intercept drainage around a field. 4.Soil moisture contents were affected by both the amount of rainfall and water-table depths, however, the moisture content for top soil showed higher correlation with the amount of rainfall while that for subsoil with water-table depths.

  • PDF

Changes of soil water content and soybean (Glycine max L.) response to groundwater levels using lysimeter

  • Lee, Sanghun;Jung, Ki-Yuol;Chun, Hyen-Chung;Choi, Young-Dae;Kang, Hang-Won
    • Proceedings of the Korean Society of Crop Science Conference
    • /
    • 2017.06a
    • /
    • pp.299-299
    • /
    • 2017
  • Due to the climate changes in Korea, the numbers of both torrential rain events and drought periods have increased in frequency. Water management practice against water shortage and flooding is one of the key interesting for field crop cultivation, and groundwater often serves as an important and safe source of water to crops. Therefore, the objective of this study is to evaluate the effect of groundwater table levels on soil water content and soybean development under two different textured soils. The experiment was conducted using lysimeter located in Miryang, Korea. Two types of soils (sandy-loam and silty-loam) were used with three groundwater table levels (0.2, 0.4, 0.6m). Mean soil water content during the soybean growth period was significantly influenced by groundwater table levels. With the continuous groundwater level at 0.2m from the soil surface, soil water content was not statistically changed between vegetative and reproductive stage, but the 0.4 and 0.6m groundwater table level was significantly decreased. Lower chlorophyll content in soybean leaves was found in shallow water table treatment in earlier part of the growing season, but the chlorophyll contents were non-significant among water table treatments. Groundwater table level treatments were significantly influenced on plant available nitrogen content in surface soil. The highest N contents were observed in 0.6m groundwater table level. It is probably due to the nitrogen loss by denitrification as the result of high soil water content. The length and dry weight of primary root was influenced by groundwater level and thus the highest length and dry weight of root were observed in 0.6m water table level. This result showed that soybean root growth did not extend below the groundwater level and increased with the depth of groundwater table level. The results of this study show that the management of groundwater level can influence on soil characteristics, especially on soil water content, and it is an important practice of to reduce yield loss caused by the water stress during the crop growing season.

  • PDF

Test for the TOPMODEL′s Ability to Predict Water Table Depths of the Transient Saturation Zones which Are Formed on the Steep Hillslope (급사면에 형성된 일시적 포화대의 지하수면깊이에 대한 TOPMODEL의 예측능력 검증)

  • An, Jung-Gi
    • Journal of Korea Water Resources Association
    • /
    • v.36 no.6
    • /
    • pp.1035-1046
    • /
    • 2003
  • In order to evaluate the TOPMODEL's prediction ability for spatial distribution of water table depths, two major assumptions and governing equation of water table depth are tested. For the test, data of hydrological observations are used and a soil survey is made in the steep hillslope with thin soils. Responses of water table and hydraulic properties of soil are coincident with two major assumptions of the TOPMODEL's such as water table gradient parallel to the local topographical slope and exponential decline in transmissivity with depths. Soil texture and the decline rate of transmissivity(f) we homogeneous in space at the 0∼0.3m depths of the soil of the hillslope, but they are heterogeneous in space below its 0.3m depths due to the vertical change of soil texture and the ‘f’. It is shown that the TOPMODEL's equation can be used for simulating distribution of water table depth at the depths with uniform values of the 'f'.

Sediment Properties and Growth of Phragmites australis in Mud Tidal Flat (조간대 저토 환경과 갈대의 생장 특성)

  • Min, Byeong Mee
    • Journal of the Korean Society of Environmental Restoration Technology
    • /
    • v.14 no.3
    • /
    • pp.57-69
    • /
    • 2011
  • This study examined the relationship between Phragmites australis' growth and sediment properties at mud tidal flat of Donggum-ri, Gilsang-myeon, Gangwha-gun, Incheon city. Field survey was carried out from May, 2010 to October, 2010. Water content, soil texture, electric conductivity and water table depth for sediment, density, height, dry weight and flowering for P. australis were examined at several plots from the starting point (the coastal embankment) to the end point of the two populations. The result was as follows. Firstly, the water table increased along distance from the embankment at one line (N-line) but was similar at the other line (S-line) in a P. asustralis population. Water tables were higher out of than within a P. australis population at two populations. Secondary, in N-line, the height and dry weight of P. australis decreased along the distance from embankment but, in S-line, those were similar in its population. P. australis' growth was dependent on electric conductivity at lower layer (water table level) rather than upper one (the surface). Thirdly, density of P. australis changed during growing season and was similar in a population, except for the end point of patch. In summary, the growth and distribution of P. australis were dependent on salt content of tidal flat's sediment (water table level) and this was affected by fresh water of the inland.

A Study on Stability of Earthquake in Estuary Barrage through Shaking Table Test (실내 진동대 실험을 통한 하구둑 구조물의 내진 안정성에 관한 연구)

  • Shin, Eun-Chul;Kang, Hyoun-Hoi;Ryu, Byung-Hyun
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2010.09b
    • /
    • pp.38-44
    • /
    • 2010
  • Shaking table tests were performed to reproduce the dynamic behavior of estuary barrage and its subbase soil which can be potentially damaged during earthquake loading. For understanding the vibration effect to the ground during earthquake, the model was formulated with 1/300 scale of prototype estuary barrage and subbase soil. Scott and Iai(1989) proposed the law of the similarity for similar experimental conditions. The laboratory model shaking table test was conducted under the vibration condition of simulated earthquake of 0.154g. The horizontal displacement on the structure was measured during the shaking table test. The pore water pressure was also monitored for the underground layers of soil. The field horizontal displacement and the pore water pressure can be predicted by using the results of the laboratory shaking table test.

  • PDF

Effect of Water Table Depth in Different Soil Texture on Quality of Barley and Wheat Grain (토성별 지하수위가 밀, 보리의 품질에 미치는 영향)

  • 이홍석;구자환
    • KOREAN JOURNAL OF CROP SCIENCE
    • /
    • v.40 no.3
    • /
    • pp.278-284
    • /
    • 1995
  • This experiment was performed to characterize the optimum water table level for the grain quality, seed germination and diastic power of barley(var. Olbori) and wheat(var. Grumil). Olbori and Grumil grew in the 550 liter plastic pot that filled with silt loam or sandy loam. During the whole growth period, the underground water level adjusted to be 20, 30, 40, 50 and 70cm. Filled grain ratio and specific gravity were not affected by soil texture and water table. Low level of water table caused the increase of 1,000 grain weight in wheat and barley, but soil texture didn't. Crude protein content tended to be high as the water table level was high, especially in wheat. Change in crude protein content was affected by underground water level more than soil texture. And the affection was slightly higher in sandy loam than silt loam, but the difference was small. The higher level of water table led to the lower crude lipid content in barley and wheat grain. Crude lipid content of both wheat and barley grain grown in sandy loam was higher than those grown in silt loam. As the water table level down, the ash content of barley and wheat grain tend to increase, especially in sandy loam. Wheat flour yield was not affected by soil texture. It was about 65% at 20cm of water level and above 67% at 40cm water level. The seed germination of wheat and barley was more than 95% when the seeds were placed at 2$0^{\circ}C$ for three days. Regardless of soil texture, the lowest germination was seen at 20cm of water table level. And the seed germination rate increased as the underground water level became low. Above 89% of barley grains were germinated within 48 hours except 20cm level of water table in sandy loam. Diastic power of germinated barley was the lowest at 20cm of water table level, and it was almost unchanged below 30cm of water table level. And also it was not affected by soil texture.

  • PDF